Method for manufacturing long laminated polarizing plate and long laminated polarizing plate

ABSTRACT

It is an object of the invention to provide a method for manufacturing a long laminated polarizing plate having a long polarizing coating formed by coating directly on a long retardation film and to provide such a long laminated polarizing plate. The present invention relates to a method for manufacturing a long laminated polarizing plate comprising a long retardation film having a slow axis in its longitudinal direction and a long polarizing coating placed on the retardation film and having an absorption axis or a transmission axis in an in-plane direction at an angle of 25 to 65° to the slow axis direction of the long retardation film, the method comprising the steps: (A) preparing a long retardation film having a slow axis in its longitudinal direction and having an Nz coefficient of 1.5 or less, wherein the Nz coefficient is expressed by the formula (nx−nz)/(nx−ny), wherein nx is a maximum in-plane refractive index of the film, ny is an in-plane refractive index of the film in a direction perpendicular to the direction in which nx is obtained, and nz is a refractive index of the film in its thickness direction; (B) rubbing the long retardation film, which is obtained in the step (A), in an in-plane direction at an angle of 20 to 70° to the longitudinal direction while feeding the long retardation film; and (C) forming a coating of a liquid crystal compound solution in an isotropic phase state on the rubbed surface of the long retardation film obtained in the step (B) and solidifying the coating to form a long polarizing coating in which the liquid crystal compound is oriented.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of copending U.S. patent applicationSer. No. 13/883,904, filed on May 7, 2013, which is a U.S. NationalStage entry of International Application No. PCT/JP2012/070918, filed onAug. 17, 2012, which claims priority to Japanese Patent Application No.2012-174090, filed on Aug. 6, 2012 and Japanese Patent Application No.2011-236202, filed on Oct. 27, 2011, the entirety of which isincorporated herein by reference.

TECHNICAL FIELD

The invention relates to a method for manufacturing a long laminatedpolarizing plate including a long retardation film and a long polarizingcoating and also relates to a long laminated polarizing plate.

BACKGROUND ART

A known example of a laminated polarizing plate is a circularlypolarizing plate including a linearly polarizing plate and a retardationfilm placed thereon and having an in-plane retardation of ¼ wavelength(also referred to as “λ/4 plate”). For example, such a circularlypolarizing plate is used in liquid crystal displays, organicelectroluminescence (EL) displays, etc.

There are known various methods for manufacturing a circularlypolarizing plate. For example, a known method includes forming alaminate of a linearly polarizing film and a λ/4 plate made of a pieceof obliquely stretched polymer film to produce a circularly polarizingplate in the form of a roll (see for example Patent Document 1). Such acircularly polarizing plate can be continuously produced using rollersand thus can be produced with high productivity.

Unfortunately, the manufacturing method disclosed in Patent Document 1involves bonding the linearly polarizing film and the λ/4 plate togetherwith an adhesive or the like. At present, there is no known longlaminated polarizing plate having a polarizing coating formed directlyon a retardation plate such as a λ/4 plate or no known method formanufacturing such a long laminated polarizing plate.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP-A-2002-22944

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

It is an object of the invention to provide a method for manufacturing along laminated polarizing plate having a long polarizing coating formedby coating directly on a long retardation film and to provide such along laminated polarizing plate.

Means for Solving the Problems

As a result of earnest study in view of the problems, it has been foundthat a process including rubbing a long retardation film with an Nzcoefficient of 1.5 or less in a specific direction while feeding thelong retardation film, forming a coating of a liquid crystal compoundsolution in an isotropic phase state on the rubbed surface of the longretardation film, and solidifying the coating can orient the moleculesof the liquid crystal compound in a direction substantially parallel tothe rubbing direction and can form a long polarizing coating directly onthe long retardation film with no adhesive or the like interposedtherebetween.

The present invention relates to a method for manufacturing a longlaminated polarizing plate comprising a long retardation film having aslow axis in its longitudinal direction and a long polarizing coatingplaced on the retardation film and having an absorption axis or atransmission axis in an in-plane direction at an angle of 25 to 65° tothe slow axis direction of the long retardation film,

the method comprising the steps:

(A) preparing a long retardation film having a slow axis in itslongitudinal direction and having an Nz coefficient of 1.5 or less,wherein the Nz coefficient is expressed by the formula (nx−nz)/(nx−ny),wherein nx is a maximum in-plane refractive index of the film, ny is anin-plane refractive index of the film in a direction perpendicular tothe direction in which nx is obtained, and nz is a refractive index ofthe film in its thickness direction;

(B) rubbing the long retardation film, which is obtained in the step(A), in an in-plane direction at an angle of 20 to 70° to thelongitudinal direction while feeding the long retardation film; and

(C) forming a coating of a liquid crystal compound solution in anisotropic phase state on the rubbed surface of the long retardation filmobtained in the step (B) and solidifying the coating to form a longpolarizing coating in which the liquid crystal compound is oriented.

The manufacturing method of the invention can orient the molecules ofthe liquid crystal compound in a direction substantially parallel to therubbing direction and can form a long polarizing coating directly on thelong retardation film. Thus, the long laminated polarizing plateobtained by the manufacturing method of the invention includes the longretardation film and the long polarizing coating placed directly on thelong retardation film with no adhesive layer interposed therebetween.

In the manufacturing method of the invention, the liquid crystalcompound solution in an isotropic phase state is preferably a lyotropicliquid crystal compound solution diluted to a concentration lower thanan isotropic-phase-to-liquid-crystalline-phase transition concentration.According to this feature, the solvent can be removed by drying so thatphase transition can occur to cause the orientation of the liquidcrystal compound, which makes it possible to simplify the manufacturingprocess.

In the manufacturing method of the invention, the rubbing in the step(B) is preferably performed by bringing a rotating rubbing roller intocontact with the long retardation film being fed. According to thisfeature, the rubbing direction can be controlled by controlling thedirection and the rotational speed of the rubbing roller, and therubbing can be uniformly performed.

The invention also relates to a long laminated polarizing plate,comprising:

a long retardation film having a slow axis in its longitudinaldirection; and

a long polarizing coating having an absorption axis or a transmissionaxis in an in-plane direction at an angle of 25 to 65° to the slow axisdirection of the long retardation film, wherein

the long retardation film has an Nz coefficient of 1.5 or less, whereinthe Nz coefficient is expressed by the formula (nx−nz)/(nx−ny), whereinnx is a maximum in-plane refractive index of the film, ny is an in-planerefractive index of the film in a direction perpendicular to thedirection in which nx is obtained, and nz is a refractive index of thefilm in its thickness direction,

the long retardation film has a surface rubbed in an in-plane directionat an angle of 20 to 70° to the longitudinal direction, and

the long polarizing coating is formed by coating directly on the rubbedsurface of the long retardation film.

The long laminated polarizing plate of the invention can be made thinnerbecause it has no adhesive layer between the long retardation film andthe long polarizing coating placed thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a schematic diagram showing an embodiment of themanufacturing method of the invention;

FIG. 1(b) is a cross-sectional view along the A-A′ line in FIG. 1(a);

FIG. 2(a) is a cross-sectional view showing an embodiment of the longlaminated polarizing plate of the invention; and

FIG. 2(b) is a plan view schematically showing an embodiment of the longlaminated polarizing plate of the invention.

MODE FOR CARRYING OUT THE INVENTION

1. Method for Manufacturing Long Laminated Polarizing Plate

The invention is directed to a method for manufacturing a long laminatedpolarizing plate. The long laminated polarizing plate includes a longretardation film having a slow axis in its longitudinal direction and along polarizing coating placed on the long retardation film and havingan absorption axis or a transmission axis in an in-plane direction at anangle of 25 to 65° to the slow axis direction of the long retardationfilm. The method includes the steps (A), (B), and (C) described below.

(1) Step (A)

The step (A) is the step of preparing a long retardation film having aslow axis in its longitudinal direction and having an Nz coefficient of1.5 or less, wherein the Nz coefficient is expressed by the formula(nx−nz)/(nx−ny), wherein nx is the maximum in-plane refractive index ofthe film, ny is the in-plane refractive index of the film in a directionperpendicular to the direction in which nx is obtained, and nz is therefractive index of the film in its thickness direction.

Such a long retardation film is used as a substrate to which the liquidcrystal compound solution described below is to be applied. The use ofsuch a substrate makes it possible to orient the molecules of the liquidcrystal compound in such a manner that the direction of their long axis(the direction of the absorption axis represented by 12 in FIG. 2(b)) issubstantially parallel to the rubbing direction (represented by 7 inFIG. 2(b)). In this context, the term “substantially parallel” meansthat the angle between the long axis direction and the rubbing directionis about 0°±5°.

Some types of liquid crystal compounds are oriented in such a mannerthat the direction of their molecular long axis is substantiallyperpendicular to the rubbing direction. In this case, the molecules areoriented in such a manner that the direction of their short axis (thedirection of their transmission axis) is substantially parallel to therubbing direction. In this context, the term “substantially parallel”means that the angle between the short axis direction and the rubbingdirection is about 0°±5°.

The Nz coefficient of the long retardation film is 1.5 or less,preferably from 0 to 1.2, more preferably from 0 to 0.5. Thus, examplesof the long retardation film include long retardation films satisfyingthe relations nx>ny>nz, nx>ny=nz, nx>nz>ny, and nz=nx>ny, respectively.When the Nz coefficient is 1.5 or less, the in-plane orientation of themolecules that form the long retardation film is relatively small, whichsuggests that the liquid crystal compound can easily move so that thelong axis direction (or short axis direction) of the molecules of theliquid crystal compound can be oriented substantially parallel to therubbing direction.

Means for preparing the long retardation film is typically a method ofstretching a long polymer film in such a manner that it can have a slowaxis in its longitudinal direction. The Nz coefficient can be adjustedto an appropriate value by controlling the stretch ratios in thelengthwise (longitudinal) direction and in the transverse direction inthe process of stretching the long polymer film. For example, a largerNz coefficient can be obtained by stretching in the longitudinaldirection and stretching at a higher stretch ratio in the transversedirection, and a smaller Nz coefficient can be obtained by stretching inthe longitudinal direction and stretching at a lower stretch ratio inthe transverse direction or shrinking in the transverse direction. Thestretch ratio may be appropriately determined depending on the type ofthe film material used or the desired Nz coefficient.

The long retardation film may be made of any material capable ofproviding an Nz coefficient in the above range. Examples of such amaterial include, but are not limited to, cycloolefin resin, celluloseresin, acrylic resin, polycarbonate resin, polyester resin, etc. Inparticular, cycloolefin resin is preferred, and norbornene resin is morepreferred.

The thickness of the long retardation film is preferably, but notlimited to, 20 to 200 μm.

In the manufacturing method of the invention, the long polarizingcoating may be placed on the long retardation film with no adhesivelayer interposed therebetween. However, an adhesion facilitating layer,such as a polyurethane resin layer, with a thickness of few microns maybe formed on the surface of the long retardation film so that the longretardation film can have improved adhesion to the long polarizingcoating.

When a long circularly polarizing plate is obtained, the in-planeretardation {(nx−ny)×(thickness)} of the long retardation film ispreferably from 120 to 160 nm, more preferably from 130 to 150 nm. Whenthe long polarizing coating described below is deposited on the longretardation film so that the angle between the absorption ortransmission axis of the polarizing coating and the slow axis of theretardation film is an angle of 25 to 65°, a long elliptically orcircularly polarizing plate can be obtained. The long retardation filmmay be a single layer or composed of a plurality of layers. The longretardation film may also contain any other layer such as apressure-sensitive adhesive layer.

(2) Step (B)

As shown in FIG. 1 or 2, the step (B) is the step of rubbing the longretardation film 1, which is obtained in the step (A), in an in-planedirection at an angle of 20 to 70° (angle α in the drawing) to thelongitudinal direction 6 while feeding the long retardation film 1 (in afeed direction 8). In this step, the rubbing is a process of rubbing thesurface of the long retardation film 1 with a rubbing cloth or the likefor the orientation of the liquid crystal molecules 11 described below.

A feature of the invention is that the liquid crystal molecules 11 areoriented in a direction coincident with the rubbing direction 7. In somecases, however, completely parallel or perpendicular relationship cannotbe achieved. Thus, the rubbing direction 7 should be set wider,specifically, set in the range of the desired long polarizing coating 10absorption or transmission axis angle ±5° (namely, in the range of 20 to70°) so that the resulting long polarizing coating 10 can have anabsorption or transmission axis in either one in-plane direction at anangle of 25 to 65° to the slow axis direction 5 of the long retardationfilm 1.

A preferred embodiment of the rubbing method is more specificallydescribed with reference to FIG. 1(a). As mentioned above, the rubbingis performed while the long retardation film 1 is fed. In the process offeeding the long retardation film 1, a first guide roller 3 and a secondguide roller 4 support the long retardation film 1 while they arerotating in contact with the back surface of the long retardation film1. The first guide roller 3 and the second guide roller 4 may be of anytype or size without limitation. In general, they are made of rubber ormetal and 10 to 500 mm in diameter. The first guide roller 3 and thesecond guide roller 4 may be the same or different.

The rubbing is performed using a rubbing roller 2, which comes intocontact with the front surface of the long retardation film 1 being fed.The rubbing roller 2 is configured to be movable up and down in thevertical direction, so that the predetermined angle and the pushingdepth described below are adjustable.

The predetermined angle of the rubbing roller 2 refers to the anglebetween the rotation axis 2 a of the rubbing roller 2 and thelongitudinal direction (namely, feed direction) of the long retardationfilm 1, which is set at 90° +α (α=20 to 70°). When the angle between therotation axis 2 a and the longitudinal direction of the long retardationfilm 1 is in this range, the rubbing direction can make an in-planeangle of α° to the longitudinal direction (see FIG. 1(a)).

The pushing depth 9 of the rubbing roller 2 is appropriately set so thatthe liquid crystal molecules can be oriented in the rubbing direction.The pushing depth 9 is preferably from 10 to 50 mm. When the pushingdepth 9 is in this range, the liquid crystal molecules can be easilyoriented in a direction coincident with the rubbing direction 7, whichis preferred. In this context, as shown in FIG. 1(b), the pushing depth9 means the amount of pushing the rubbing roller against the retardationfilm from the starting point (the amount of change in position), whereinthe starting point is the position of the long retardation film beforethe rubbing roller comes into contact with it.

The rubbing cloth may be any raising cloth without limitation. Thematerial, shape, or other features of the raising cloth may beappropriately selected depending on the material to be rubbed. Forexample, the raising cloth is usually made of cotton, rayon, nylon,triacetate, or the like. The type, size, or other features of therubbing roller 2 are also not restricted.

A series of procedures for the rubbing are further described in detail.For example, the long retardation film 1 is supported under apredetermined tension between the first guide roller 3 and the secondguide roller 4. On the other hand, the rubbing roller 2 is held onstandby above (not in contact with) the long retardation film 1. Therubbing roller 2 is then rotated in the horizontal direction, and thedesired rubbing angle is set as shown in FIG. 1. Subsequently, therubbing roller 2 is lowered to a predetermined position to come intocontact with the upper surface of the long retardation film 1. The longretardation film 1 is fed in the direction from the guide roller 3 tothe guide roller 4 under a predetermined tension at a predetermined rateusing an appropriate feeding and driving apparatus (not shown), and therubbing roller is rotated at a predetermined speed, so that the uppersurface of the long retardation film 1 is continuously rubbed.

The feed speed of the long retardation film 1 and the rotational speedof the rubbing roller are not restricted. Preferably, the rotationalspeed of the rubbing roller 2 is sufficiently higher than the feed speedof the long retardation film 1.

(3) Step (C)

The step (C) is the step of forming a coating of a liquid crystalcompound solution in an isotropic phase state on the rubbed surface ofthe long retardation film obtained in the step (B) and solidifying thecoating to form a long polarizing coating in which the liquid crystalcompound is oriented.

The liquid crystal compound may be a lyotropic or thermotropic liquidcrystal compound. Preferably, the liquid crystal compound is a lyotropicliquid crystal compound. As used herein, the term “lyotropic liquidcrystal compound” refers to a liquid crystal compound that can bedissolved in a solvent to form a liquid crystal compound solution andcan undergo a phase transition from an isotropic phase to a liquidcrystalline phase (or vice versa) as the concentration of its solutionchanges. In this context, the concentration at which thenon-liquid-crystalline state (isotropic phase) changes to the liquidcrystalline state (liquid crystalline phase) is referred to as the“isotropic-phase-to-liquid-crystalline-phase transition concentration.”As used herein, the term “thermotropic liquid crystal compound” refersto a liquid crystal compound that can thermally undergo a phasetransition from an isotropic phase to a liquid crystalline phase (orvice versa). In this context, the temperature at which thenon-liquid-crystalline state (isotropic phase) changes to the liquidcrystalline state (liquid crystalline phase) is referred to as the“isotropic-phase-to-liquid-crystalline-phase transition temperature.”

In the invention, therefore, the “liquid crystal compound solution in anisotropic phase state” may be specifically a liquid crystal compoundsolution diluted to a concentration lower than theisotropic-phase-to-liquid-crystalline-phase transition concentration ormay be specifically a liquid crystal compound solution having atemperature higher than the isotropic-phase-to-liquid-crystalline-phasetransition temperature and not being liquid crystalline (or being in anisotropic phase).

The lyotropic liquid crystal compound solution for use in the inventionusually contains a lyotropic liquid crystal compound and a solvent inwhich the lyotropic liquid crystal compound is soluble. For example, thelyotropic liquid crystal compound may be an azo compound, ananthraquinone compound, a perylene compound, a quinophthalone compound,a naphthoquinone compound, a melocyanine compound, or the like. Inparticular, an azo compound is preferred.

For example, the azo compound may be an azo compound represented by thefollowing general formula (1).

In formula (1), Q₁ is an aryl group which may have any substituentgroup; Q₂ is an arylene group which may have any substituent group; R isa hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetylgroup, a benzoyl group, or a phenyl group (these groups may have anysubstituent groups); and M is a counter ion.

M is a counter ion and is preferably a hydrogen atom, an alkali metalatom, an alkali earth metal atom, a metal ion or a substituted orunsubstituted ammonium ion thereof. Examples of a metal ion include, forexample, Li⁺, Ni²⁺, Fe³⁺, Cu²⁺, Ag⁺, Zn²⁺, Al³⁺, Pd²⁺, Cd²⁺, Sn²⁺, Co²⁺,Mn²⁺, or Ce³⁺ and the like. When the counter ion M is a multivalent ion,a plurality of azo compounds share one multivalent ion (counter ion).

The azo compound is preferably represented by the following generalformula (2). In the formula (2), R and M are the same as those in theformula (1). X is a hydrogen atom, a halogen atom, a nitro group, acyano croup, an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 4 carbon atoms, or —SO₃M group.

For example, the azo compound can be produced by the method described inJP-A-2009-173849.

The solvent may be of any type capable of dissolving the lyotropicliquid crystal compound. Preferably, the solvent is a hydrophilicsolvent. Examples of the hydrophilic solvent include water, alcohols,cellosolves, and any mixture thereof. In particular, water is preferred.The solvent may also contain a water-soluble compound such as glycerinor ethylene glycol.

The concentration of the lyotropic liquid crystal compound solution islower than the isotropic-phase-to-liquid-crystalline-phase transitionconcentration. In other words, the lyotropic liquid crystal compoundsolution is in a non-liquid-crystalline state (isotropic phase). Whensuch a lyotropic liquid crystal compound solution is used, the liquidcrystal compound can be easily oriented parallel or perpendicular to therubbing direction without being influenced by the shear stress duringthe coating process.

The concentration of the lyotropic liquid crystal compound solution maybe at any level lower than theisotropic-phase-to-liquid-crystalline-phase transition concentrationwithout limitation. In general, the concentration of the lyotropicliquid crystal compound solution is preferably from 1 to 10% by weightbased on the total weight of the solution. The lyotropic liquid crystalcompound solution may be applied by any method capable of forming auniform coating. For example, the solution may be applied using a wirebar, a gap coater, a comma coater, a gravure coater, a tension webcoater, a slot die, or the like.

After the lyotropic liquid crystal compound solution is applied, theconcentration of the solution is changed so that the solution undergoesa phase transition from an isotropic phase to a liquid crystallinephase, and thus the liquid crystal molecules are oriented to form a longpolarizing coating. The method for changing the concentration of thesolution may be, but not limited to, a natural drying method or a heatdrying method.

The thermotropic liquid crystal compound solution for use in theinvention usually contains a thermotropic liquid crystal compound and asolvent in which the thermotropic liquid crystal compound is soluble.The solvent and applying method of the thermotropic liquid crystalcompound solution are same as those of the lyotropic liquid crystalcompound solution.

When the thermotropic liquid crystal solution is used, the solutionundergoes a phase transition from an isotropic phase to a liquidcrystalline phase as its temperature changes, so that the liquid crystalmolecules are oriented to form a long polarizing coating. Thetemperature for the phase transition may be appropriately selecteddepending on the type of the liquid crystal compound used.

The concentration of the liquid crystal compound in the long polarizingcoating formed in the step (C) is preferably from 80 to 100% by weightbased on the total weight of the long polarizing coating. The thicknessof the long polarizing coating is preferably from 0.1 to 10 μm, morepreferably from 0.1 to 5 μm.

The long polarizing coating formed in the step (C) exhibits absorptiondichroism at at least one wavelength in the visible light region and hasan absorption axis in an in-plane direction. The absorption dichroism isobtained when the liquid crystal compound is oriented in the longpolarizing coating. The direction of the absorption or transmission axisof the long polarizing coating makes an angle of 25 to 65° to thelongitudinal direction.

2. Long Laminated Polarizing Plate

The long laminated polarizing plate of the invention includes a longretardation film 1 having a slow axis in its longitudinal direction anda long polarizing coating 10 having an absorption axis or a transmissionaxis in an in-plane direction at an angle of 25 to 65° to the slow axisdirection of the long retardation film 1, wherein the long retardationfilm has an Nz coefficient of 1.5 or less, wherein the Nz coefficient isexpressed by the formula (nx−nz)/(nx−ny), wherein nx is the maximumin-plane refractive index of the film, ny is the in-plane refractiveindex of the film in a direction perpendicular to the direction in whichnx is obtained, and nz is the refractive index of the film in itsthickness direction; the long retardation film has a surface rubbed inan in-plane direction at an angle of 20 to 70° to the longitudinaldirection; and the long polarizing coating is formed by coating directlyon the rubbed surface of the long retardation film.

As used herein, the term “formed by coating directly on” means that thelong polarizing coating is formed directly on the long retardation filmwith no adhesive. As used herein, the term “long” means that the lengthis sufficiently larger than the width, and preferably, the length is tentimes or more the width.

The long laminated polarizing plate of the invention can be manufacturedby the method of the invention described above, while it may bemanufactured by other methods. The materials, the thickness, and otherfeatures of the long retardation film and the long polarizing coatingmay be those described above.

The long laminated polarizing plate of the invention preferably has alength of 300 m or more. The long laminated polarizing plate preferablyhas a total thickness of 20 to 200 μm.

The angle between the slow axis direction of the long retardation filmand the absorption or transmission axis direction of the long polarizingcoating (the angle β in FIG. 2(b)) is preferably from 25 to 65°, morepreferably from 30 to 60°. When the angle is set in this manner, a longcircularly polarizing plate can be obtained, with which circularlypolarized light can be produced from linearly polarized light incidentin a specific direction at any wavelength in the visible light region(wavelengths from 380 to 780 nm), which is preferred.

3. Applications

For example, the long laminated polarizing plate obtained according tothe invention may be used in liquid crystal displays or organic ELdisplays.

EXAMPLES

Hereinafter, the invention is described with reference to the examplesbelow, which however are not intended to limit the invention.

<Measurement Methods>

In each of the examples and the comparative examples described below,the measurement methods described below were used for determination andevaluation.

(1) Measurement of Thickness

The thickness was measured using a digital gauge (PEACOCK (product name)manufactured by OZAKI MFG. CO., LTD.).

(2) Determination of Slow Axis, In-Plane Retardation, and Nz Coefficientof Long Retardation Film and Angles of Absorption Axis and TransmissionAxis of Long Polarizing Coating

These were determined at 23° C. using KOBRA-WPR (trade name)manufactured by Oji Scientific Instruments. The measurement wasperformed at a wavelength of 590 nm.

Production Example 1 Preparation of Aqueous Lyotropic Liquid CrystalSolution

In accordance with a conventional method (“Riron Seizo Senryo Kagaku(Theoretical production Dye Chemistry)” Fifth Edition, Yutaka Hosoda(published on Jul. 15, 1968, GIHODO SHUPPAN Co., Ltd.), pages 135 to152), a monoazo compound was produced by diazotizing and coupling4-nitroaniline and 8-amino-2-naphthalene sulfonic acid. The obtainedmonoazo compound was diazotized by a conventional method in the samemanner and was further subject to diazotization and coupling reactionwith 1-amino-8-naphthol-2,4-disulfonate lithium salt. An obtained roughproduct including an azo compound having the following structuralformula (3) was salted out with lithium chloride to obtain the azocompound having the following structural formula (3).

The azo compound of the aforementioned structural formula (3) wasdissolved in ion-exchange water to prepare an aqueous lyotropic liquidcrystal solution of 8% by weight.

Example 1

A cycloolefin polymer film was stretched to form a long retardation filmhaving a slow axis parallel to its longitudinal direction and having anNz coefficient of 0.4. The resulting long retardation film had anin-plane retardation of 140 nm.

While the resulting long retardation film was fed, the surface of thefilm was rubbed by the same method as shown in FIG. 1(a) in such amanner that the rubbing direction (a) was 45° (the pushing depth of therubbing roller: 15 mm, rubbing cloth: rayon cloth). The 8% by weightlyotropic liquid crystal aqueous solution in an isotropic phase preparedin Production Example 1 was then applied to the rubbed surface of thelong retardation film with a tension web coater, and the solution wasnaturally dried to form a 0.4-μm-thick long polarizing coating. Thelyotropic liquid crystal is oriented in such a manner that the long axisdirection of its molecules is substantially perpendicular to the rubbingdirection. Thus, the lyotropic liquid crystal is oriented in such amanner that its transmission axis direction is substantially parallel tothe rubbing direction. The longitudinal direction of the resulting longcircularly polarizing plate was at an angle of 42° to the transmissionaxis direction of the long polarizing coating. Thus, the transmissionaxis direction was deviated by an angle of 3° from the rubbingdirection.

Example 2

A cycloolefin polymer film was stretched to form a long retardation filmhaving a slow axis parallel to its longitudinal direction and having anNz coefficient of 1.0. The resulting long retardation film had anin-plane retardation of 140 nm.

A long circularly polarizing plate was prepared by the same method as inExample 1, except that the obtained long retardation film with an Nzcoefficient of 1.0 was used. The longitudinal direction of the resultinglong circularly polarizing plate was at an angle of 41° to thetransmission axis direction of the long polarizing coating. Thus, thetransmission axis direction was deviated by an angle of 4° from therubbing direction.

Comparative Example 1

A cycloolefin polymer film was stretched to form a long retardation filmhaving a slow axis parallel to its longitudinal direction and having anNz coefficient of 1.6. The resulting long retardation film had anin-plane retardation of 140 nm.

A long circularly polarizing plate was prepared by the same method as inExample 1, except that the obtained long retardation film with an Nzcoefficient of 1.6 was used. The longitudinal direction of the resultinglong circularly polarizing plate was at an angle of 27° to thetransmission axis direction of the long polarizing coating. Thus, thetransmission axis direction was deviated by an angle of 18° from therubbing direction.

Comparative Example 2

A cycloolefin polymer film was stretched to form a long retardation filmhaving a slow axis parallel to its longitudinal direction and having anNz coefficient of 1.8. The resulting long retardation film had anin-plane retardation of 140 nm.

A long circularly polarizing plate was prepared by the same method as inExample 1, except that the obtained long retardation film with an Nzcoefficient of 1.8 was used. The longitudinal direction of the resultinglong circularly polarizing plate was at an angle of 25° to thetransmission axis direction of the long polarizing coating. Thus, thetransmission axis direction was deviated by an angle of 20° from therubbing direction.

DESCRIPTION OF REFERENCE SIGNS

1 Long retardation film

2 Rubbing roller

2 a Rotation axis

3 First guide roller

4 Second guide roller

5 Slow axis direction

6 Longitudinal direction

7 Rubbing direction

8 Feed direction

9 Pushing depth

10 Long polarizing coating

11 Liquid crystal molecule

12 Direction of absorption axis (Long axis direction of molecule) whatis claimed is:

1. A long laminated polarizing plate, comprising: a long retardationfilm having a slow axis in its longitudinal direction; and a longpolarizing coating having an absorption axis or a transmission axis inan in-plane direction at an angle of 25 to 65° to the slow axisdirection of the long retardation film, wherein the long retardationfilm has an Nz coefficient of 1.5 or less, wherein the Nz coefficient isexpressed by the formula (nx−nz)/(nx−ny), wherein nx is a maximumin-plane refractive index of the film, ny is an in-plane refractiveindex of the film in a direction perpendicular to the direction in whichnx is obtained, and nz is a refractive index of the film in itsthickness direction, the long retardation film has a surface rubbed inan in-plane rubbing direction at an angle of 20 to 70° to thelongitudinal direction, and the long polarizing coating is formed bycoating a solution of a liquid crystal compound in an isotropic phasestate directly on the rubbed surface of the long retardation film, thelong laminated polarizing plate has an absorption axis or a transmissionaxis deviated by an angle of about 0°±5° from the in-plane rubbingdirection.
 2. The long laminated polarizing plate according to claim 1,wherein the Nz coefficient of the long retardation film is less than1.0.
 3. The long laminated polarizing plate according to claim 1,wherein the Nz coefficient of the long retardation film is from 0 to0.5.